The present invention relates to a knitting needle driving mechanism of a knitting machine, more particularly to a knitting needle driving mechanism for driving a knitting needle by using one or more piezo-electric elements.
In a jacquard knitting machine such as a jacquard circular knitting machine, a jacquard flat knitting machine or the like, there has heretofore been used a knitting needle driving mechanism for transmitting a patterning procedure memorized in a memory such as a pin drum, a tape, a floppy disk or the like to an up-and-down movement of the knitting needle. For example, there has been known the knitting needle driving mechanism as illustrated in FIG. 21, a main portion of which comprises a plurality of fingers 50 arranged in parallel to one another. In this kind of knitting needle driving mechanism, the finger 50 slides by signals supplied from the memory to allow a jack 51 engaging with a lower end of the knitting needle to move toward a center of a knitting cylinder 52, whereby a cam butt 53 on a lower portion of the jack 51 disengages from a rising cam 54.
On the other hand, a high-speed jacquard knitting machine has recently been desired. In order to cope with such a high-speed knitting machine, it is also necessary to speed up the response of the knitting needle driving mechanism. However, the knitting needle driving mechanism constituted so as to slide the fingers as described above has a limit to an increase in response speed or in sliding speed of the fingers. It is possible to obtain a high-speed knitting machine by increasing the number of the fingers without an increase in response speed. However, the increased number of the fingers results in a large-sized knitting needle driving mechanism, and causes the difficulty of arranging the knitting needle driving mechanism in a narrow space.
In the meantime, the same applicant as that of the present invention proposed a knitting needle driving mechanism comprising a plurality of swingable fingers in Japanese Patent Unexamined Publication No. 60-22485/1985, entitled "Knitting Needle Driving Mechanism of Circular Knitting Machine". This knitting needle driving mechanism can achieve a rapid response speed compared to conventional ones having the sliding-type fingers in wide use, and therefore can easily cope with the high-speed knitting machines. Further, this also serves to miniaturize the knitting needle driving mechanism and to decrease the power consumption thereof.
However, in the knitting needle driving mechanisms having the above sliding-type and swing-type fingers, the fingers are slid or swung by utilizing an attraction force and a repelling force from an electromagnet. Namely, the fingers are slid or swung by applying an electric current to both the poles of the electromagnet in such a manner that the poles of the electromagnet are changed from plus to minus, respectively, or vice versa. Therefore, the response speed of the knitting needle driving mechanism activated by the electromagnet has a limit caused by a function of the electromagnet itself, and an optimum high speed of the electromagnet is around 80 cycles per second. On the other hand, the power consumption efficiency of the electromagnet is about 1% and the remainder of the electric current is consumed as heat or the like, and hence there is the problem in that the total consumption of the electric power is extremely high when the knitting needle driving mechanism having the electromagnet is used.
Consequently, this kind of knitting needle driving mechanism can not be used for, for example, a circular knitting machine for knitting pantyhose having 240 knitting needles and a rotational speed of 220 rpm. Accordingly, in the existing circumstances, the rotational speed of the circular knitting machine is decreased to a speed corresponding to an ordinary response speed of the conventional knitting needle driving mechanism, when pantyhose are knitted.
Then, the same applicant as that of the present invention proposed a piezo-electric knitting needle driving mechanism in which a needle is driven by bending a finger by means of piezo-electric elements, in place of the above knitting needle driving mechanism of the knitting machine using the electromagnet (Japanese Patent Unexamined Publication No. 62-28451/1987).
As illustrated in FIGS. 14 an 15, the finger 21 of the knitting needle driving mechanism comprises a plate 24 having an attaching portion 22 for attaching the finger to a housing, at an end of the plate, a guiding portion 23 engaging with a finger butt of a knitting needle or a jack and attached to the end of the plate opposite to the attaching portion 22, and piezo-electric elements 28 and 29 attached to an upper face and an under face of the plate 24 and connected to a controller 27 (refer to FIG. 19) with lead wires 25 and 26.
As illustrated in FIG. 19, the attaching portions 22 of the fingers 21 (eight fingers are superimposed in the embodiment shown in FIG. 19) are supported in a rear wall 31 of the housing 30 of the knitting needle driving mechanism 20 and the attaching portions 22 serve as fulcrums of the bending motion of the fingers 21.
Turning to FIG. 19, the reference numerals 32, 33 and 34 designate a front wall of the housing 30, an upper wall thereof and a lower wall thereof, respectively. As shown in FIG. 20, the front wall 32 of the housing 30 is provided with an opening 35 for allowing the guiding portions 23 of the fingers 21 to protrude therethrough, and further, grooves 36 each of which has a width corresponding to a rising distance and a descending distance of the guiding portion 23.
FIG. 16 is a perspective view showing a state in which the guiding portion 23 of the finger 21 slides along the above groove 36 of the front wall 32. As shown in FIGS. 14 and 16, the guiding portion (guiding element) 23 is formed in an angled shape and attached to an end 24' of the plate 24 by means of an adhesive.
The operation of this finger 21 will hereunder be described with reference to FIGS. 17 and 18.
FIG. 17 shows a state in which a pulse is not applied to the piezo-electric element of the finger 21, and FIG. 18 shows a state in which a pulse is applied to the piezo-electric element, thereby bending the finger 21. In the state shown in FIG. 17, the finger butt 56 of the jack 51 or the knitting needle itself engages with the guiding element 23 to push the jack 51 to the right, so that a rising cam butt 53 arranged on a lower end of the jack 51 can not engage with a rising cam 54. As a result, the jack and accordingly the knitting needle engaging with an upper portion of the jack are not subjected to rising movement, which results in no formation of a knitting loop by this knitting needle. On the other hand, in the state illustrated in FIG. 18, the guiding element 23 of the finger 21 does not enter a moving path of a finger butt 56 of the jack 51 due to the bending of the finger 21, so that the jack 51 keeps its vertical position. As a result, the rising cam butt 53 of the jack 51 engages with the rising cam 54 to push the jack 51 upward, and the knitting operation is applied to the knitting needle engaging with the upper portion of the jack 51.
Thus, according to the above knitting needle driving mechanism having the fingers each using the piezo-electric elements, the piezo-electric element has a rapid response speed, and therefore it is possible to apply a pulse with high frequency to the element. For example, when a pulse of 240 cycles is applied to the element, the knitting needle can be driven at a high speed three times the speed (usually 80 cycles) of known knitting needle driving mechanisms operated by electromagnets. This means that the number of the fingers can be decreased to one-third of that of the fingers used in the known knitting needle driving mechanisms, for the knitting machines on which the same jacquard clothes are knitted. Further, if there is used this knitting needle driving mechanism which has the same number of the fingers as that of the fingers of the conventional knitting needle driving mechanisms, it is possible to knit a jacquard cloth having a pattern three times complicated in comparison to that of clothes knitted by using the conventional knitting needle driving mechanisms, namely, to knit a jacquard cloth on a knitting machine in which a product of the number of the knitting needles and a rotational speed of the knitting cylinder (in the case of a circular knitting machine) is three times that of conventional knitting machines.
The finger of this knitting needle driving mechanism is constituted by a thin plate and one or more piezo-electric elements. It is therefore possible to decrease the height necessary for arranging one finger in the driving mechanism and the width thereof, compared to the conventional fingers actuated by the electromagnets. Hence, also when the same number of the fingers are used in the knitting needle driving mechanism, the knitting needle driving mechanism itself can be further miniaturized in size. As described above, since this knitting needle driving mechanism is small in size and has a high response speed, it becomes easy to provide a jacquard knitting function also to a circular knitting machine for knitting pantyhose in which space it has previously been difficult to dispose the knitting needle driving mechanism for knitting a jacquard cloth.
As described above, however, in this knitting needle driving mechanism, the guiding portion 23 formed in an angled shape is attached to the end 24' of the plate 24, and the attaching portion 22 of the finger 21 is supported in the rear wall 31 of the housing 30. Namely, the finger 21 is cantilevered and bent as illustrated in FIG. 18. As a result, if a pulse with higher frequency is applied to the piezo-electric elements 28 and 29 to increase a response speed higher, the engagement of the jack with the butt or the like is not stabilized in some cases. Further, if the ceramic material is used to form the piezo-electric elements 28 and 29, the impact produced when the guiding portion 23 collides with the butt is transmitted to the piezo-electric elements 28 and 29 to induce strain therein, which possibly results in the damage of the piezo-electric elements 28 and 29 to reduce the lifetime thereof, because the finger 21 is cantilevered and the guiding portion 23 is bonded to the end 24' of the plate 24, in addition to the essential chipping easiness of the ceramic material.
Then, for the purpose of improving the knitting needle driving mechanism described above, the present inventor has further proposed a piezo-electric knitting needle driving mechanism in which both ends of a plate having one or more piezo-electric elements are supported in walls of a housing accommodating the knitting needle driving mechanism (Japanese Patent Application No. 63-19619/1988).
A knitting needle driving mechanism according to the invention the above-mentioned Japanese Patent Application No. 63-19619/1988 will hereunder be described with reference to FIGS. 11 to 13 in comparison to a piezo-electric knitting needle driving mechanism similar to that described above as shown in FIG. 14.
FIG. 12 is a perspective view showing a main portion of the housing of the knitting needle driving mechanism according to the present invention, and FIG. 11 is a perspective view, partly in cross section, of an embodiment of the knitting needle driving mechanism according to the present invention.
As illustrated in FIG. 12, a plurality of lateral grooves 17 for supporting plates are formed on each of inner surfaces of both side walls 16 and 16 of a plate supporting portion 15 of the housing 14. Both ends 80 and 80 of the plate 8 are inserted into the grooves 17 formed on both the walls 16 and 16, and piezo-electric elements 9 are attached to an upper face and an under face of the plate 8, thereby constituting a piezo-electric body 2, as shown in FIG. 11.
In the knitting needle driving mechanism shown in FIG. 14, the attaching portion 22 formed at an end of the plate 24 to which the piezo-electric elements 28 and 29 are attached is supported in the rear wall 31 of the housing 30 of the knitting needle driving mechanism 20 as illustrated in FIG. 19, and serves as a fulcrum of the bending motion of the finger 21. Namely, the finger 21 is supported in a cantilever form and bent in this cantilever form.
In contrast, in the knitting needle driving mechanism shown in FIG. 11, both the ends 80 and 80 of the plate 8 to which the piezo-electric elements 9 are attached is supported by the plate supporting portions 15 in the housing 14 of the knitting needle driving mechanism, not in the cantilever form. In both cases, when a pulse is applied to the piezo-electric element, a piezo-electric phenomenon occurs on the piezo-electric element, and mechanical strain causes mechanical vibration of the plate, thereby bending the plate.
In the former, the bending is carried out in the cantilever form. However, in the latter, the bending is achieved in the form in which both the ends of the plate are supported. The latter can therefore attain the stabilized bending motion even on application of a pulse with high frequency and the improvement of the response speed. Further, the piezo-electric elements 9 bonded to the plate 8 are difficult to be broken, and hence their lifetime is prolonged.
Furthermore, in the knitting needle driving mechanism illustrated in FIG. 14, the guiding portion 23 engaging with the butt of the knitting needle or the jack is attached to the end 24' of the plate 23.
In contrast, in the knitting needle driving mechanism shown in FIG. 11, a finger 5 is mounted not on the plate 8, but on the piezo-electric element 9. Namely, a rear end portion 5A of the strip-like finger 5 is mounted on a center of an upper face of the piezo-electric element 9 so that the finger 5 is arranged about perpendicularly to the longitudinal axis of the plate 8. A back face of the rear end portion 5A of the finger 5 is bonded to the upper face of the piezo-electric element 9 through an elastic member 10. Accordingly, the mechanical vibration or the movement of the plate 8 is well transmitted to the finger 5, and the impact produced when a front end portion 5B of the finger 5 engages with the butt of the jack or the like is decreased, thereby being capable of cushioning external strain imparted to the piezo-electric element 9. Also, the finger 5 is easily detached from the plate 8 and replaced with a new one.
In addition, in the knitting needle driving mechanism shown in FIG. 11, a fulcrum portion 5C of the bending motion of the finger 5 is fixed to a finger fixing portion 18, and a fixing portion 180 serves as a fulcrum of the bending motion of the finger 5. The finger fixing portion 18 is vertically installed adjacent to a plate supporting portion 15 of a housing 14, as illustrated in FIG. 12. As shown in FIG. 13, the finger 5 is provided with a hole in the crosswise direction of the finger 5, and each of right and left end walls 18A and 18B of the finger fixing portion 18 are also provided with a hole. A shaft 6 is inserted into the hole of the finger 5, and both ends of the shaft 6 are fitted into the holes of the right and left end walls 18A and 18B, respectively. Then, screws 7 and 7 are threaded in from both the ends of the shaft 6 to fix the shaft 6 to the end walls 18A and 18B.
Consequently, when the movement of the piezo-electric element 9 attached to the plate 8 is transmitted to the above fulcrum 180 through the rear end portion 5A attached to the piezo-electric element 9 of the finger 5, it is required to amplify that movement. For this reason, an amplifying portion 5D for amplifying the movement of the finger 5 is provided, elongating from the fulcrum 180 to the front end portion 5B of the finger 5, thereby forming the finger 5 longer. There can be achieved the effect that the impact is cushioned by the middle portion of the finger 5 due to the long finger when the front end portion 5B of the finger 5 engages with the butt of the jack or the like. Further, since the finger 5 is thus fixed to the finger fixing portion 18, the impact produced when the front end portion 5B of the finger 5 engages with the jack 51 does not reach the piezo-electric element, which results in the difficulty in damage of the piezo-electric element. The lifetime thereof can therefore be prolonged.
However, in the knitting needle driving mechanism shown in FIG. 11, the finger 5 is attached perpendicularly to the longitudinal axis of the piezo-electric body 2 composed of the plate 8 and the piezo-electric elements 9, so that the piezo-electric body 2 is increased in width and the plate supporting portion 15 of the housing 14 is required to be also increased in width, which results in a large-sized knitting needle driving mechanism and causes the difficulty of arranging the knitting needle driving mechanisms in a narrow space for certain kinds of knitting machines. As described above with respect to FIG. 12, several knitting needle driving mechanisms are arranged around a knitting cylinder. The number of knittings accompanied by the rotation of the knitting cylinder and the knitting speed depend upon the number of the knitting needle driving mechanisms arranged. Hence, the miniaturization of the knitting needle driving mechanism is an important problem.
Further, in the knitting needle driving mechanism shown in FIG. 11, the rear end portion 5A of the finger 5 is attached to the surface of the piezo-electric element 9 bonded to the plate 8 in such a manner that the finger 5 is overlapped on the piezo-electric body composed of the plate 8 and the piezo-electric element 9 bonded thereto. This causes the knitting needle driving mechanism to increase in size in the direction of the height of the housing, when the knitting needle driving mechanism is accommodated in the housing 14. In addition, the rear end portion 5A of the finger 5 is attached to the surface of the piezo-electric element 9 through the elastic material 10, so that the knitting needle driving mechanism is further increased in size and the clearance between the fingers 5 is enlarged when a large number of plates and fingers are accommodated in the housing.
Furthermore, in the knitting needle driving mechanism described above, the load of the finger 5 is liable to fall on the piezo-eletric element 9 due to the attachment of the finger 5 to the surface of the piezo-eletric element 9, though the finger 5 is fixed by the finger fixing portion 18. Hence, when voltage is applied to the piezo-eletric element 9 to achieve the bending motion, the bending motion may be disturbed and there is the possibility that the piezo-electric element 9 is broken at its attached position in long-term use.
Moreover, in the knitting needle driving mechanism described above, the finger 5 is provided with the amplifying portion 5D, thereby forming the finger longer, and the elastic material 10 is disposed between the piezo-electric element 9 and the finger 5, for cushioning the impact produced when the front end portion 5B of the finger 5 engages with the butt or the like. In this case, the torque developed when the front end portion 5B of the finger 5 engages with the butt or the like to drive the knitting needle can not but be reduced, and the elastic material is easily deteriorated because of being formed of elastic rubber.